1. Field of the Invention
This invention is directed in general to a system for sensing and memorizing spatial and time-domain distribution of measurable events, and more particularly to a system which employs an array of contact cells (sensor elements) to provide an indication of spatial and time-domain distribution of events on a surface.
2. Description of the Background Art
The existing systems measuring distribution of events on a surface (including tactile sensors) are devices consisting of an array of cells (mechanical, electrical, optoelectronic, magnetic, pneumatic, etc.) capable of sensing contacts with external objects, and in some cases capable of measuring magnitude of these contacts. Even if memory devices are incorporated into these cells, a system can only memorize spatial distribution of sensed events. For example, this can be used in touch-sensitive pads to create digital copies of hand-written signatures. However, the system itself cannot memorize the dynamic (time-domain) properties of the sensed events, i.e. it is impossible to extract from the content of the memory in what sequence the cells have been activated (contacted). As a result, the system requires support of auxiliary devices (usually a control unit and external memory buffers) for memorizing time-domain distribution of sensed events. Examples of such devices are disclosed in U.S. Pat. Nos. 4,441,097, 4,953,410, 5,010,772 and 5,325,442. This solution requires complex wiring and control. The manufacturing cost of such devices becomes inhibitively high and therefore limited only to restricted areas of applications.
It would therefore be highly desirable to improve the existing systems and methods for sensing, capturing, and memorizing time-domain and spatial distribution of events for including particular technological innovations to eliminate the significant disadvantages as stated earlier, and to further improve the overall system performance.
Prior arts as illustrated by Anderson et.al can not function autonomously to memorialize the spatial events and require further external support of timer clock, current meter and address decoder circuit. Namely, the tactile sensor as shown in the prior arts can be understood as a two dimensional grid array wherein each grid location comprises a capacitor cell. During the human contact of a selective grid location, capacitor cell will be charged or discharged according to the characteristic of the power source. Furthermore, since a current will be injected across the wire pair which interconnect the grid location, a current meter and a address decoding circuit will be employed in order to measure and identify the contact grid location. Provided with external clock timer, said grid location can be memorialized along with the time instance when the contact is happening.
In our invention, each contact cell comprises a sensor, a controller, and at least one memory element, wherein during the moment when said sensor detects a contact event at that cell location, an impulse is being transmitted to said controller, and said controller uses said impulse as a control signal for allowing said memory element to store a charging signal at that moment of the contact event, wherein said charging signal is the output from a binary counter, input of said counter is triggered by a clock generator, therefore by setting a suitable clock frequency according to the requirement of said contact event, magnitude of said charging signal can change proportionally according to the elapse of the time. Accordingly said memory element can store a charging signal representing time coordinate of said contact event. Likewise, the magnitude of said charging signal can change proportionally to the magnitude of said contact event, therefore a second memory element at that cell location would be able to store a charging signal representing spatial domain coordinate of said contact event.
The distinctive advantages of our invention is that, in a natural sensing environment, e.g., pressure sensing of a wind tunnel, power consumption need to be conserved, our invention provides a low cost alternative to sense and preserve spatial event and the time domain information without the requirement of external timer clock, address decoding circuit, and current meter.
It is therefore an object of the present invention to provide an improved system which employs an array of contact cells (sensor elements) to sense, capture, and memorize spatial and time-domain distribution of contact events.
It is further an object of the present invention to apply said system for a wide range of contact events including those being a result of mechanical, pneumatical, optical, electrical, acoustic, magnetic, or alike action.
It is further an object of the present invention to improve said system for autonomous maintaining said memorized contact events without any memory device or control unit being external to said contact cells.
It is still further an object of the present invention to utilize said system for extracting and measuring dynamic description including acceleration, speed, or alike for said memorized contact events.
It is still further an object of the present invention to allow said improved system for a multiple dimensional implementation.
These and other objects and advantages are provided by:
(i) incorporating into the said system a source of charging/loading signal, which generates a signal changing correspondingly to the elapsed time and/or correspondingly to the number of sensed contact events;
(ii) incorporating into said contact cells a memory device which memorizes the current value of the said signal at the moment of cell activation (contact event).
Optionally, a second memory device can be incorporated into said contact cells in order to memorize magnitude of sensed contact events.
Once the data have been memorized, the system can preserve and maintain data for quite a long period without any external connection.
If adequate material technology can be applied, the system can be manufactured in extremely economical, miniaturized and robust manner, and therefore applicable for wide range of application.
Since the system memory preserves both the time-domain and spatial co-ordinates of sensed contact events, it is possible to extract a detailed dynamic description of the registered phenomena. For example, the speed and acceleration of a pen drawing hand-written images can be measured.